Syllabus

Download the syllabus here.

Scores

Here are all your scores so far. You are only identified by the last four digits of your DU ID. Please report any mistakes in the scores to me.

Presentations

Homework

  1. Due September 19

    a) Decipher the following message. I have used an affine monoalphabetic cipher. Look at frequencies of characters, digraphs and trigraphs before you make a guess.

    werddgqmdurofevmtsdjsodxgrdfehmdfmducmwmbgsrxewgzygsddfedieroigzifiengzumoureobmweobgszcur
    sdmongqqurqerfgszngrqzsrgrdfmdzmexcunnceatmqzmedmlmziuomtsdudiertmcurxrscturqnaxsnnerxwfun
    mdfmzmezmngdogbgdfmzsruksmwgzygsdoerxksuzyaineoomodgtmfexeddfmqacrgwexeaodfmazmrgdbgzmhmza
    grmvnsodfmaennzmksuzmednmeodbgzdabuhmcursdmogzerfgszgbagszducmqacoerxodsxugofehmexgvdmxdfm
    detededmifruksmerxcexmuddfmuzgwrtaexxurqcsouimksuvcmrderxhezugsomlmziuomodgdfmuzineoomotsd
    dfmducmxurdmzhenodavuiennazmceurdfmoecmubbgnngwmxigzzmidnadfmmlmziuomofgsnxbeduqsmmhmrdfmc
    godbudqactsrrumo
    

    b) Choose an English text with 500 characters. Write down the 5 most common digraphs in the text. Write down the 5 most common characters in the text. Prepare a graph as follows: Take the most common character, say X. Calculate the RELATIVE frequency of X after 100, 200, 300, 400, 500 characters. Plot the 5 values into the graph and connect them by lines. Using different colors, repeat for the remaining four characters.

    c) Do the same as b) but for an article in a foreign language. Tell me which language was used. Point out the main differences in your statistical analysis between English and the foreign language.

  2. Due September 26

    Decipher the following ciphertext, obtained with a monoalphabetic cipher. Briefly describe the your work and email me the description and the plaintext. You don't have to transcribe the plaintext into proper English with spaces and punctuation. Work alone!

    rdxpdissxdvsyhkfsydhkqhfsyvbqhkjpfpvdhksbiftqcpsyrdiinyrdjbdiiuvderqshsutadrfsyedhjppcvprp
    hkrapmdjrvpjrsuvpdiqrfqjrapvpnyrqhmqjqnipfsykcvsndnifiqxpdkpmqepradrapicjfsyjppbyeabsvpsuq
    rjeqphrqjrjtsvxqhldrepvhrappyvscpdhsvldhqodrqshusvhyeipdvvpjpdveaadmpbdkpjsbpcvslvpjjqhrad
    rkqvperqshtqrarapdicadbdlhprqejcpervsbprpvtaqeaadjnpphvqkqhldnsdvkrapqhrpvhdrqshdijcdepjrd
    rqshjqheprtsrasyjdhkdhkpipmphcafjqeqjrjnpiqpmpradrbphrdipgpveqjpqhniqhkhpjjvpuiperjrapvpdi
    qrfsusyvyhqmpvjpshifdnsyrusyvcpvephrsutaqeabdhqupjrjdjrapxqhksubdrrpvdhkphpvlftpedhcpvepqm
    pbsvpradhjpmphrfcpvephreshjqjrjsujsediipkkdvxphpvlfcafjqeqjrjjdfdhkbsvpradhrtphrfcpvephrqj
    kdvxbdrrpvhpqrapvsutaqeaaybdhjedhkqvperifkprperjsudvnyrjeqphrqjrjuppiepvrdqhqrbyjrpgqjrcdv
    rifnpedyjpsuraplvdmqrfqrpgpvrjshrapmqjqnipyhqmpvjpraqjtppxepvhjeqphrqjrjcyniqjapkdhdhdifjq
    jsukdrduvsbrapjcpervsbprpvtaqeakprperjjyndrsbqecdvrqeipjeshjrdhrifnsbndvkqhlpdvrarapfqheiy
    kppgeppkqhlifvdvpdhrqbdrrpvcdvrqeipjradredhvpjyiruvsbrapnvpdxksthsukdvxbdrrpvrapfdvpediipk
    csjqrvshjdijsxhsthdjdhrqpipervshjrapfadmprapjdbpbdjjdjpipervshjnyrpipervshjadmpdhpldrqmpea
    dvlpdhkcsjqrvshjadmpdcsjqrqmpeadvlpjeqphrqjrjnpiqpmpkdvxbdrrpvesiiqkpjjciqrrqhlqhrscdqvjsu
    pipervshjdhkcsjqrvshjjsrapdnqiqrfrspgdbqhpcsjqrvshjqhkprdqiesyikapicqhcvsmqhlrappgqjrpheps
    ukdvxbdrrpv
    
  3. Due October 3

    Decipher the following ciphertext, obtained with a Vigenere cipher. Show work! Identify the author and title of the plaintext.

    asbncyageanuxtmggzrbyonttgrlfthsdjzbjccedrvwqlmedqrwbtlfnseiicnkuirwigydwinguyxodrfwlfwfth
    zxwsueilrvcoyippyvcyiztsslndjmciyvugydnwvqaffmgjvjocydxzrwyogkllboylnftrgliycflefwbpjmxrgh
    xqcsjvrrzecytefkytmodqzrhwsdttehmphfthfdppntpxvqftygdjnvwjnttlrkywxiwegdnlwmhynoawuzrivvoa
    jahiqwimyfwiclweodthvpuryaueuxapjqchhooxmgrlnvqpmqtsadheccjipoineeilruyhuehszhnsczvlbzygyd
    xrgkyljbteedhnyauxulmxuowmahqscowgnxmpxytxbuyrudsmgpicymixrqntpqacjkcwyuvemhxocdtggosfjipv
    qdntnrdvvwmaiexxvrhhuexqzhxtuftplrpplynsjqcquzrmrgnsufxwnzceczbsgliyczprvqmeuzieswycqmghgk
    yquzrcjdmnizumepyocfhwjhyaqmhfelyquzsssfifletwyrqtqmiguhxtnrdvfrgpgucyghmdiytaudnthrteeeoe
    gagivqqzhptvjhuccqsegoyyafwavwbzvetvilhrcfhhhofxihtqrqntnggrrggjyktwhsiynttsgkycinyipwmthf
    wiphfwueamtknyiuhinwncuoiiqpsyifxgrdhofadovqaeifwisoizluhejvygydpprqicgajwedndndpzrumthsxx
    gkyjbmsmfvopxrgszwbpqqapjkcnbxpcwxmequilvqptyiiszbltatiiihhebqcaulfpcspdrgnsykrezhoaczivbr
    jdbggvvhxwsixxuuugyzdyfhspmmaphuyovkilrvwphfdjgkyxymijergebuhmguybougiqponbqujbunlhppxghhe
    cacxbvwllqilrpuhukxxzlasntpzreyphtppsdhsiggtrubljetzrquybajvsrltwajpqwuvynjxvpjplrtggqieya
    uxvpymyrdvrluruucgnvnxsqnifxjhudsaudntnttrfdqnizushqxpxmchnpukypbigkydqqttbinsybtrqxffgtph
    vqwcymhiqlhprftrgesyymgpldsllppwnqueodppprhdycjiafytnekiyrwtnklefdfdiyjgujlpuftvoxnhbmiqnl
    hwspxwgxlmypbijdmebqxhrdnsufweqsycwqexvefjxqhgrqxpxucsjrvdydkiqzcebiwegkiclagmglmyyqsprvme
    iepcgkuecfhrrwbplqmxehgtnklefiicgqsssdwcyeriawiqaxxxghlthshxrhflvajxniiznucprqaebrgszkichf
    dlbuhebqwseqmfjipvqdhonttyagycypvirycoyzipldmvyqcefwblnaueedtzlxxordlltageyvitnetizhxxuehc
    nqxsymkcgdjplucksuixnttiqjythfdefrftxmchouilxeivhfnflqpfbyytnipwnsjphpthgruhyuvlgblzxaufed
    mduzsxuhqsixtlvvmpxmhmgvqfhsilerorbfwinll
    
  4. Due October 10th

    I have used a Playfair cipher with the default parameters. The plaintext is:

    oh yo us im pl et on sa id sh et he nw em us ta ll fo ur di eo fh un ge ry ou ha db et te
    rp la ne th ec of fi ns fo ru sb ut sh el ef th im no pe ac et il lh ec on se nt ed sa yi
    ng ah bu ti sh al lr eg re tt he po or ch il dr en th et wo ch il dr en ho we ve rh ad no
    tg on et os le ep fo rv er yh un ge ra nd so th ey ov er he ar dw ha tt he st ep mo th er
    sa id to th ei rf at he rg re th el we pt bi tt er ly an ds ai dt oh an se lw ha tw il lb
    ec om eo fu sb eq ui et gr et he ls ai dh ed on ot cr yi wi ll so on he lp yo ua nd as so
    on as th ei rp ar en ts ha df al le na sl ee ph eg ot up pu to nh is co at an du nb ar ri
    ng th eb ac kd oo rs li pp ed ou tt he mo on sh on eb ri ll ia nt ly an dt he wh it ep eb
    bl es wh ic hl ay be fo re th ed oo rs ee me dl ik es il ve rp ie ce st he yg li tt er ed
    so br ig ht ly ha ns el st oo pe dd ow na nd pu ta sm an yi nt oh is po ck et as it wo ul
    dh ol da nd th en go in gb ac kh es ai dt og re th el be co mf or te dd ea rs is te ra nd
    sl ee pi np ea ce go dw il ln ot fo rs ak eu sa nd so sa yi ng he we nt to be da ga in
    

    The corresponding ciphertext is:

    ku ua lr ce vq bi ak je nv rv bi vo tj ae lr nb gv rm ro vn ab rp yk lb ju kr do xa bi ib
    fh ye ia kx mi mr sc ij rm or we gk rv is ms kx ce ka vm mn bi vs uv mi ak ei kc av je ln
    ty od og cn rv ey us bl so xg vo hm ko kp vs hj ai kx bi rb kp vs hj ai uk sb li ou ny ka
    xw ak bi er si mv rm sh os ud yk lb jo dy re kx al eh os vo oj xj do xg vo wi mv eb kx os
    je nv kb kx iv ws bn vo wu so kx is sb xc et xg os yu nd vj en xn ku nd ei gs do xb vs ge
    mi be ab rq we ml lk bi uw bi vo se en hx av ak bk kf ln st gv re ak vo qv ua yo dy ej re
    ak ej kx iv fh oj ai iw do pj ey si dn es bv vx bl bk qh hq kb kd ve km bn nd hy ta oj sk
    ty kx am mn nh bh wj sv vp av kr xg vo eb ak rv ak am sk gv ne kc yu nd xn vo rx nc mv am
    eg ie rx ni vu nj ma rm so kx av bh wj bv ea vy nt ie vs li fh vi im wi vo uq sv xg os av
    re ow tl xk yu do ij is wi bh vm hp br dn dy hq nb fe nd ln kc ku ve hm it bi ej nc rb gy
    hx eu yn dy kx ai ub nk wt mn hu ie en xn bu so kx is ma km cm ko ib hp ao wj ve ib jo dy
    es bv vc cd ao im ub xj vs yi bk rm wj on ol je dy re je ln ty vo sb kc kb ma yn yb nk
    

    Your task is to reconstruct as much of the Playfair square as possible. Please return the square with the letter "a" in the top left position. Explain how you solved the problem. Don't forget to check that you found the correct square!

  5. Due October 24

    Here is the ciphertext obtained with a 2x2 Hill's System.

    mkekgkvtzgmlomoebvquesfbqffhqfelkoaomwlqarwokyqfjqrybytqktamzopkaxykfzzcnmrlsqfhmwfwzoaxyk
    vwmlfwquiqfhktoyciaxykdofwzorlsqfhinamnmmlfwquiqfhktiegxjscaquivfhwzwrhsfqlpfwrasjqfkdgxlb
    wzuvhsewrazopkvswofhqfelkoaogchuacgxudsqtastwrqajrbianvymobsgxhuitobsdktampkcggcmdeasjwomd
    easjwozgmlmtwremomwqktkpelkyghywsectpibvcnmbcgcasugcwoddfwrefbxmkmxpfwzcxpyxquivfufdktkpye
    dgccwemonnksamdagxczkdaqyxindgqfmtwrmlfwankayxopmbsdxpfwaxgkvtgcnmngommoddfwzcxpyxvsrequiv
    fhkygharzclkkdaqoumbsqoeghsegklqfhktqecaokshznmqqmohlqjeryxpyxuyfhfhohcogcfwquivfhanikmlkt
    amnmnassktufivrpgcfhwrzcdavsankayxmlcygcqmkyelohsqfhkygharzclkquivjqkdaqeryxkmghtumlbiwhwz
    ypvsfhktyoohkdaqyxindgqfktanmdjolpqfjqtuymaqanxpcykyelcgcaiqanmkcmanxpcyctgcegmoddfwzcxpyx
    gxcvyxkmomajuvcykyelohzcnnuvlqjewrfhyskdaqouuvczanbskdmipertfhqfelkoaogpctrsaxykvwbmbyjrbi
    anhzeefhyxmdfhaifhyxmlgwcffwxmombluvaqaihdyxwqktkphuignofwzkacqffmleygyrccelveaqohfwrsmlnm
    iqudgcugfhkyfhcgoelkhfqgjejqnexpfwpexycawoktjqfhohsqraza
    

    What is the matrix A used in the encryption? What is the inverse of A? What is the plaintext? Show your work!

    Hint: TH and HE correspond to two of the 3 most common dighraphs in the ciphertext (not necessarily in that order).

  6. Due November 5

    Decipher the following message encrypted with Baby RSA, using the public key (n,e) = (4495423, 31113). Note that you are only able to do this because the primes used to obtain n are small. Describe your work!

    dswebjwrbjcmswayjalc
    
  7. Due November 14

    a) Consider the binary code C={00000000,11100000,00100101,00011100}. i) What is the distance of C? ii) How many errors can C detect/correct? iii) Decode the received message 11001100, if possible.

    b) Construct a binary code C of length 8, size 4 and distance 5.

    c) Is there a binary code of length 8, size 7 and distance 5?